>You can only remove the energy actively until these short-lived products decay to the point where air cooling is sufficient to keep them at a safe temperature.

>You can only remove the energy actively until these short-lived products decay to the point where air cooling is sufficient to keep them at a safe temperature. this is my point - necessity for active removal of energy. The closest thing to what i was talking about seems to be molten salt reactors where energy producing reaction goes only when salt is pumped through the core/moderator. If something goes wrong - the valves open and the salt is dumped [gravitationally] into the tanks which can be large enough to allow for passive air cooling of the secondary decay energy.